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Mechanical forces are central to developmental, physiological and pathological processes (1). However, limited understanding of force transmission within sub-cellular structures is a major obstacle to unravelling molecular mechanisms. Here we describe the development of a calibrated biosensor that measures forces across specific proteins in cells with piconewton (pN) sensitivity, as demonstrated by single molecule fluorescence force spectroscopy (2). The method is applied to vinculin, a protein that connects integrins to actin filaments and whose recruitment to focal adhesions (FAs) is force-dependent (3). We show that tension across vinculin in stable FAs is ~2.5 pN and that vinculin recruitment to FAs and force transmission across vinculin are regulated separately. Highest tension across vinculin is associated with adhesion assembly and enlargement. Conversely, vinculin is under low force in disassembling or sliding FAs at the trailing edge of migrating cells. Furthermore, vinculin is required for stabilizing adhesions under force. Together, these data reveal that FA stabilization under force requires both vinculin recruitment and force transmission, and that, surprisingly, these processes can be controlled independently., Focal adhesions (FAs) are complex intracellular linkages between integrins and the F-actin cytoskeleton that both transmit and respond to mechanical forces. FAs show complex mechanosensitivity such that they form or [...]

Integrin-linked kinase (ILK) in mammals has been found to be necessary for polarizing the epiblast, cell adhesion, and controlling actin accumulation. A t the peri-implantation stag e, m i ce lacking ILK expression die because they do not polarize the epiblast and cavitate. ILK is a focal adhesion component that interacts with the cytoplasmic domains of integrins. It also recruits adaptor proteins that link integrins to the actin cytoskeleton and phosphorylates serine /th reonine kinases PKB/Akt and GSK-3(be ta).

The ability of cells to sense and respond to mechanical forces is central to a wide range of biological processes and plays an important role in numerous pathologies. The molecular mechanisms underlying cellular mechanotransduction, however, have remained largely elusive because suitable methods to investigate subcellular force propagation were missing. Here, we review recent advances in the development of biosensors that allow molecular force measurements. We describe the underlying principle of currently available techniques and propose a strategy to systematically evaluate new Förster resonance energy transfer (FRET)-based biosensors. [ABSTRACT FROM AUTHOR]

By interacting with components of the human host, including extracellular matrix (ECM) proteins, Streptococcus pneumoniae has evolved various strategies for colonization. Here, we characterized the interaction of pneumococci with the adhesive glycoprotein vitronectin and the contribution of this protein to pneumococcal uptake by host cells in an integrin-dependent manner. Specific interaction of S. pneumoniae with the heparin-binding sites of purified multimeric vitronectin was demonstrated by flow cytometry analysis. Host-cell-bound vitronectin promoted pneumococcal adherence to and invasion into human epithelial and endothelial cells. Pneumococci were trapped by microspike-like structures, which were induced upon contact of pneumococci with host-cell-bound vitronectin. αvβ3 integrin was identified as the major cellular receptor for vitronectin-mediated adherence and uptake of pneumococci. Ingestion of pneumococci by host cells via vitronectin required a dynamic actin cytoskeleton and was dependent on integrin-linked kinase (ILK), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt), as demonstrated by gene silencing or in inhibition experiments. In conclusion, pneumococci exploit the vitronectin-αvβ3-integrin complex as a cellular receptor for invasion and this integrin-mediated internalization requires the cooperation between the host signalling molecules ILK, PI3K and Akt. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the molecular optomechanics approach revealing functional relevance of force transduction across talin and desmoplakin. It mentions that results of the study reveal a central role of talin and desmoplakin as mechanical linkers in cell adhesion structures and demonstrate that molecular optomechanics, a powerful tool to investigate the molecular details of mechanobiological processes.

Mechanoelectrical transduction is mediated by the opening of different types of force-sensitive ion channels, including Piezo1/2 and the TREK/TRAAK K 2P channels. Piezo1 curves the membrane locally into an inverted dome that reversibly flattens in response to force application. Moreover, Piezo1 forms numerous preferential interactions with various membrane lipids, including cholesterol. Whether this structural architecture influences the functionality of neighboring membrane proteins is unknown. Here, we show that Piezo1/2 increase TREK/TRAAK current amplitude, slow down activation/deactivation, and remove inactivation upon mechanical stimulation. These findings are consistent with a mechanism whereby Piezo1/2 cause a local depletion of membrane cholesterol associated with a prestress of TREK/TRAAK channels. This regulation occurs in mouse fibroblasts between endogenous Piezo1 and TREK-1/2, both channel types acting in concert to delay wound healing. In conclusion, we demonstrate a community effect between different structural and functional classes of mechanosensitive ion channels., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)